![]() Period − It is represented as the sum of on-time and off-time of PWM signal.ĭuty Cycle − It is represented as the percentage of time signal that remains on during the period of the PWM signal.Īs shown in the figure, T on denotes the on-time and T off denotes the off-time of signal. Off-Time − Duration of time signal is low. ![]() On-Time − Duration of time signal is high. There are various terms associated with PWM − A basic PWM signal is shown in the following figure. Pulse width modulation is basically, a square wave with a varying high and low time. PWM has many applications such as controlling servos and speed controllers, limiting the effective power of motors and LEDs. The “_timer” pointer will be set to the TCB3 due to the Nano Every having MILLIS_USE_TIMERB3 defined in the board.txt file configuration, thus placing the system timer for millis(), micros() and delay() on TCB3.Pulse Width Modulation or PWM is a common technique used to vary the width of the pulses in a pulse-train. Then in Wiring.c it sets the system TCBn timer to use the same prescalar as TCA in the CTRLA register: /* Clock selection -> same as TCA (F_CPU/64 - 250kHz) */ ![]() This means that TCA is running at 250kHz, for the default system clock of 16MHz. CTRLA = (TCA_SINGLE_ CLKSEL_DIV64_gc) | (TCA_SINGLE_ENABLE_bm) The Arduino library configures the TCA CTRLA “CLKSEL” bits to /64 in the setup_timers() function from the relevant variant.c file: // Use DIV64 prescaler (giving 250kHz clock), enable TCA timer None of the other output pins options from the ATmega4809 are routed out to physical pins on the Arduino Every.Ī major limitation with the 4809’s timer setup is that there is only one prescalar setting and it is shared across all timers. The Arduino library has TCA (“non-split” mode) mapped onto PORTB (pins 5, 9, 10) TCB0 to PF4 (pin 6) and TCB1 to PF5 (pin 3). There are two options for each of the single channels of TCB0, 1, 2 and 3, a default and alternative mapping, depending on the settings of the TCBROUTEA register. To use all six pins requires the use of “split mode” for TCA, but only pins of PORTB are actually broken out for the Nano Every anyway, so “non-split mode” is used which only applies to bits. There are six options for the three channels of TCA: they can be mapped onto pins for each of PORTA to PORTF depending on the setting of the TCAROUTEA register. Which output pins are connected to which timer channel is controlled by the ATmega4809’s PORTMUX registers (see chapter 15 in the datasheet). Note that there are many more options for the ATmega4809 itself but these are not broken out in the Arduino Nano Every.
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